Safety seating of humans in vehicles and devices moving with ever increasing speeds has been addressed in the prior art in manifold ways. Besides most commonly used seat belts and air bags, pivoting seats have been introduced to adjust the sitting position to off-vertical gravitational loads. For example, a number of aircraft and car seats have been described in U.S. Pat. Nos. 2,227,717; 3,112,955; 2,823,730; 3,357,736 that provide a pivoting movement around an axis perpendicular to a vehicle's movement direction. Such seat designs were thought to adjust a seated persons position in response to a frontal impact.
Significant dynamic gravitational load changes away from vertical orientation have been recognized also for example in fly simulating devices. There, varying centrifugal loads resulting from undulating rotational movements of the seated person are compensated by seating capsules hinging around two perpendicularly acting joints. The capsules overall center of gravity is kept in an offset to both axes such that the capsule is aligning itself with varyingly directed gravitational accelerations. In that way, gravitational loads may be experienced by a person seated in the capsule predominantly in vertical direction with respect to the person's seating position irrespective the spatial orientation of a sum gravitational acceleration vector acting from the outside via the two axes onto the capsule. See for example U.S. Pat. Nos. 2,282,763; 2,357,781; 4,898,377.
The concept of such double axes suspension of a seating capsule has been applied in the prior art to a child safety seat to be mounted in a car as described in U.S. Pat. Nos. 6,439,660 and 6,634,708 both invented by John Guenther. Guenther attempts to safely seat a child also against other than frontal vehicle impacts. Guenther as well as the above listed hinging safety seats fail to address the particularities of rotational impact response characteristics of a human seated with respect to a primary impact vector or primary impact plane of a vehicle. By not taking into account these particularities and as described in detail below and in reference to the Prior Art FIGS. 1A, 1B, most prior art hinging safety seating devices in fact expose the seated person to increased risks of neck injuries and well known head whip lashing compared to rigid safety seating systems.
The main difference between fly simulating devices and safety seating devices are gradients of acceleration and deceleration force direction changes. Such gradients may be more than a magnitude higher in case of a sudden vehicle impact during which decelerations occur in multiples of the common gravitational acceleration experienced on earth as is well known to anyone skilled in the art. In a hinged capsule or seat 11, the deceleration VXN is transferred onto the seat/capsule 11 via hinge(s) AC1, (AC2). In single hinge prior art safety seats, naturally only one hinge AC1 is employed. In double hinge prior art seating capsules, two hinges AC1, AC2 are employed. In a freely suspended seat/capsule 11, an overall center of gravity GO including the gravity centers of the seated human 100 and the seat/capsule 11 is resting vertically below the hinge(s) AC1, (AC2) in an impact initial position where only gravitational acceleration acts on the seat/capsule 11 and human.
During an impact where the vehicle is rapidly decelerated, an overall mass reaction force FXO acts in direction opposite and parallel with respect to the deceleration VXN. The overall mass reaction force FXO introduces a main torque around the hinge(s) AC1, (AC2) on the seat/capsule 11. The overall mass may include the mass of the human 100 and the seat/capsule 11. The main torque resulting from the overall mass reaction force FXO multiplied with a main normal distance DG between deceleration vector VXN and overall gravity center GO rotationally accelerates the seat/capsule 11 with the seated human 100 around the axis AC1. The main normal distance DG is the distance between the overall gravity center GO to the acting hinge AC1 in direction normal the impact deceleration VXN vector.
In the example of Prior Art FIGS. 1A, 1B, the main rotational acceleration results in a counterclockwise rotation CCR of the seat/capsule 11 and those human 100 body portions belted on the seat/capsule 11. The rotational acceleration is opposed by an overall momentum of inertia of the seat/capsule 11 and all rotationally rigidly connected portion(s) of the human 100 resulting in a response time it takes for the seat/capsule 11 to move from an impact initial orientation depicted in Prior Art FIG. 1A into a impact aligned orientation where the overall center of gravity GO is again aligned with deceleration VXN vector as depicted in Prior Art FIG. 1B.
The main human body part rigidly connected with the seat/capsule 11 may be the torso 105 commonly belted up the seat/capsule 11. Head 101, arms 103 and legs 102 hinge on the torso 105 and receive their rotational acceleration around hinge AC1 via neck 104 and respective shoulder and hip joints. The head 101 has the largest mass with its head gravity center GH being in head normal distance DH with respect to an approximate neck center NC. Head normal distance DH are is normal with respect to a resulting head mass force FRH.
At the impact initial position of Prior Art FIG. 1A, the resulting head mass force FRH is composed in a well known manner of an impact head reaction mass force FXH and a rotational acceleration head reaction mass force FTH both described in the below. As the angular speed of the seat/capsule 11 ramps up from zero at the impact initial orientation, a centrifugal head reaction mass force FCH occurs and contributes to the resulting head mass force FRH as well. At the impact aligned orientation of Prior Art FIG. 1B, rotational acceleration is down to zero and only impact head reaction mass force FXH and dependent on a residual rotational speed of the seat/capsule 11 an eventual centrifugal head reaction mass force FCH may contribute to the resulting mass force FRH.
As can be seen in Prior Art FIG. 1A, the resulting head mass force FRH is oriented clockwise with respect to the neck center NC and in head normal distance DH, which together resulting in a clockwise rotation CR that is in opposite direction than the counterclockwise rotation CCR of the sea/capsule 11 and the belted up torso 105. The neck 104 has to compensate the two opposing rotations CR, CCR which may cause excessive neck bending. As the rotational speed of the seat/capsule 11 ramps up, centrifugal head reaction mass force FCH increases, while impact head reaction mass force FXH and/or rotational acceleration head reaction mass force FTH may decrease to a point where the orientation of the resulting head mass force FXH becomes oriented also in counterclockwise direction with respect to the neck center NC. The head 101 is consequently rotated back around the neck center NC until it is stopped by the seat's/capsule's 11 upholstery. During a crash related impact, this takes places within a fraction of a second resulting in a well known whip lashing of the head, which may be significantly stronger compared to a conventionally seated child due to the initial excessive neck bending and additional centrifugal head reaction mass force FCH that is not present in a conventionally seated child's head.
The clockwise rotation CR of the head 101 resulting from the opposite rotational acceleration continues as long as the head gravity center GH remains above the neck center NC while the torso is already in counterclockwise rotation CCR. This oppositely acting head 101 tilting torque induced during the time span it takes for the head normal distance DH to decrease to zero produces an counter rotating head 101 tilting energy that may cause excessive bending of the neck 104. Once the rotation of the seat/capsule 11 and the torso 105 has progressed to the extent that the head gravity center GH moves below the neck center NC the rotational acceleration of the head 101 is reversed and the head whip lashes back. The whip lashing may be even amplified by centrifugal forces acting on the head 101 at that moment.
Also not addressed in the Prior Art is another particularity of the rotational impact response characteristic of pivotally seated human 100 that may be related to an neck center angle ON between the overall gravity center GO and the approximate neck center NC. The closer to or even worse larger than ninety degrees the neck center angle ON, the longer and initially larger are the effects of the deceleration VXN transmitted onto the neck 104. This is because the closer or larger the neck center angle ON to ninety degrees, the more the neck 104 initially moves perpendicular with respect to the deceleration VXN vector while the seat/capsule 11 rotates. This again prolongs the time span and overall amount of the deceleration VXN transmitted onto the neck center NC resulting in prolonged impact head reaction mass force FXH and ultimately increases a counter rotating head 101 tilting energy that the neck 104 has to absorb as may be well understood by anyone skilled in the art.
Referring to Prior Art FIG. 1B, another unfavorable result of the neck center angle ON being close to or larger than ninety degrees may be a non perpendicular final orientation of the neck 104 during impact aligned orientation of the seat/capsule 11 in which the overall gravity center GO is aligned with the deceleration VXN vector through the hinge AC1. The larger the neck 104 center angle ON the more the final neck 104 orientation may be out of perpendicularity.
In summary, prior art pivoting safety seats or capsules 11 may adversely effect a seated human's safety particularly against neck injuries, resulting from excessive neck bending, excessive rotating head 101 tilting energy, head whip lashing and non perpendicular final neck 104 orientation. Therefore, there exists a need for a safety seating system that minimizes the risk of excessive neck 104 bending, excessive rotating head 101 tilting energy, and head 101 whip lashing of a rotationally seated human. The present invention addresses this need.
In a real case of a vehicle crash, decelerations and eventual accelerations acting on the hinges AC1, AC2 may be of complex primarily two dimensional nature resulting from varying impact directions. Probabilities of impact directions of a passenger car known to the inventor at the time this invention was made are shown in Prior Art FIG. 2. In some cases, like during a rollover, the decelerations may even be of a three dimensional nature. Such complex primarily two dimensional and eventually even three dimensional decelerations may result in rapidly reorienting torques initiating rotational movements in varying directions around the hinges AC1, AC2. The torso 105 belted up to the capsule 11 follows these movements directly whereas the head 101 with its mass may lag behind, which again may cause undesirable neck 104 bending. The further the head gravity center GH is horizontally away from an intersection of the hinges AC1, AC2, the more violent the head 101 may dangle in such situations with respect to the belted up torso 105. Therefore, there exists a need for a safety seating system in which head 101 dangling due to multi dimensional deceleration patterns that eventually occur during a vehicle crash are kept to a minimum. The present invention addresses also this need.
Child safety seats are commonly fixed on top of the upholstery of either a rear or a front passenger seat. The inherent softness of the upholstery renders a rigid fixing of the child safety seat practically impossible. In case of a prior art child safety seat 10 having a capsule 11 double hinged via a cardan arm 12 on a base 13, the rotational movement of the capsule 11 during an impact is likely impeded by adjacent objects such as door handles, front seat backrest in case of a backseat mounting or a dashboard in case of a front seat mounting of the child safety seat 10. In addition, a deploying air bag may push the capsule 11 into an unfavorable orientation. Therefore, there exists a need for a child safety seat that may rotationally reorient itself during an impact unimpeded by eventual contact with adjacent objects and/or unimpeded by an eventually deploying air bag. The present invention addresses also this need.
The use of hinges and an eventual cardan arm 12 to rotationally hold a seat/capsule 11 with respect to the base 13 requires increased stiffness of the seat/capsule 11 to channel the extreme mass forces that may occur during a crash onto the relatively small hinges AC1, AC2 as may be clear to anyone skilled in the art. This in turn results in increased mass and momentum of inertia of the seat/capsule 11. In addition, deformation in the hinges and in the eventual cardan arm 12 need to be accounted for as well and sufficient spacing between the seat/capsule 11 needs to be provided between the individual parts that move with respect to each other. For a given installation space available in a passenger car, the size of the seat/capsule 11 is consequently limited by such spacing constraints, which in turn forces a positioning of the child close the hinges AC1, AC2 resulting in a large neck center angle ON. Therefore, there exists a need for a rotationally reorienting child safety seating system in which rotational guiding may be provided without use of hinges or intermediate structures in a direct fashion between a rotating capsule and a fixed base that provides for low momentum of inertia and maximum space of the rotating capsule and seating of the child with reduced neck center angle ON. The present invention addresses also this need.
Finally, the rotational speeds induced on a rotating seat/capsule 11 during crashes at varying impact speeds may vary with at least one order of magnitude as may be well appreciated by anyone skilled in the art. A generic brake without any means to adjust itself to the large bandwidth of rotational speeds of the seat/capsule 11 most likely will cause a stopping of the seat/capsule 11 at an unintended final orientation diminishing or even canceling the intended operation of the seat/capsule 11. Therefore, there exists a need for a braking feature that responds to varying rotational speeds of the seat/capsule 11 for an increased reorientation precision. The present invention addresses also this need.